Methamphetamine is a powerful, highly addictive stimulant used illicitly in New Zealand and around the world. It is obtained either through smuggling into the country, or by being manufactured locally in clandestine laboratories (meth labs). These meth labs may be found in residential dwellings, commercial accommodation, and even vehicles.

A dwelling can become contaminated with methamphetamine residues if the drug is manufactured or smoked within it. Smoking usually results in much lower residue levels compared with manufacture. The question that forms the basis of this report is whether, and at what level of detection, methamphetamine residue on household surfaces poses a risk to human health.

International guidelines have been developed specifically for cleaning of contaminated premises after a meth lab has been discovered. These guidelines use the detection of methamphetamine below a specified low level after remediation as evidence that other hazardous chemicals and solvents associated with traditional methamphetamine manufacturing methods have been sufficiently cleaned away.

In New Zealand, manufacturing methods have changed and now mostly eliminate the risks posed by other hazardous chemicals. Methamphetamine is therefore the primary contaminant arising from both manufacture and smoking. However, overseas guidelines developed for cleaning after manufacture have increasingly been used in New Zealand to suggest a need for methamphetamine testing more generally, regardless of whether or not manufacturing activity is suspected.

In the absence of clear scientific and health information, there has been an assumption among the general public that the presence of even trace levels of methamphetamine residue poses a health risk. An industry of methamphetamine testing and remediation companies has emerged alongside these concerns. As a result, remediation of properties considered at risk has been undertaken – sometimes at great cost.

This situation is largely unique to New Zealand – in other countries methamphetamine investigations focus mainly on identifying meth labs (or former labs), and remediating them when found. Non-meth lab contamination generally does not lead to any particular consideration or action. The question thus emerges, is the New Zealand approach over-precautionary or appropriate?